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  • 1
    Language: English
    In: Soil Science Society of America journal, 2012, Vol.76(1), pp.18-27
    Description: Accurate estimation of soil gas diffusivity (Dp/Do, the ratio of gas diffusion coefficients in soil and free air) and air permeability (ka) from basic texture and pore characteristics will be highly valuable for modeling soil gas transport and emission and their field-scale variations. From the topsoil of two Danish arable fields representing two natural clay gradients, Dp/Do and ka were measured at soil water matric potentials between −1 and −100 kPa on undisturbed soil cores. The Rosin–Rammler particle size distribution parameters α and β (characteristic particle size and degree of sorting, respectively) and the Campbell water retention parameter b were used to characterize particle and pore size distributions, respectively. Campbell b yielded a wide interval (4.6–26.2) and was highly correlated with α, β, and volumetric clay content. Both Dp/Do and ka followed simple power-law functions (PLFs) of air-filled porosity (εa). The PLF tortuosity–connectivity factors (X*) for Dp/Do and ka were both highly correlated with all basic soil characteristics, in the order of volumetric clay content = Campbell b 〉 gravimetric clay content 〉 α 〉 β. The PLF water blockage factors (H) for Dp/Do and ka were also well (but relatively more weakly) correlated with the basic soil characteristics, again with the best correlations to volumetric clay content and b. As a first attempt at developing a simple Dp/Do model useful at the field scale, we extended the classical Buckingham Dp/Do model (εa2) by a scaling factor based on volumetric clay content. The scaled Buckingham model provided accurate predictions of Dp(εa)/Do across both natural clay gradients. ; p. 18-27.
    Keywords: Clay ; Particle Size ; Topsoil ; Texture ; Prediction ; Porosity ; Models ; Soil Water ; Soil Air ; Sorting ; Air ; Particle Size Distribution ; Permeability ; Diffusivity
    ISSN: 0361-5995
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  • 2
    Language: English
    In: Agriculture, Ecosystems and Environment, Sept 15, 2012, Vol.159, p.9(10)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.agee.2012.06.021 Byline: Emmanuel Arthur (a), Per Moldrup (b), Martin Holmstrup (c), Per Schjonning (a), Anne Winding (d), Philipp Mayer (d), Lis W. de Jonge (a) Keywords: Soil contamination; Dehydrogenase activity; Clay dispersibility; Air permeability; Compression; Resilience Abstract: a* Microbial activity decreased significantly at copper concentration [approximately equal to]500mgkg.sup.-1. a* Soil compression resistance had an increasing trend with copper concentration. a* Copper contaminated soils had higher amounts of water dispersible clay. a* Clay dispersibility correlated with microbial activity in a copper contaminated field. Author Affiliation: (a) Department of Agroecology, Faculty of Science and Technology, Aarhus University, Blichers Alle 20, P.O. Box 50, DK-8830 Tjele, Denmark (b) Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Sohngaardsholmsvej 57, DK-9000 Aalborg, Denmark (c) Department of Bioscience, Aarhus University, Vejlsovej 25, DK-8600 Silkeborg, Denmark (d) Department of Environmental Science, Faculty of Science and Technology, Aarhus University. Frederiksborgvej 399, DK-4000 Roskilde, Denmark Article History: Received 23 February 2012; Revised 1 June 2012; Accepted 15 June 2012
    Keywords: Soil Pollution ; Permeability ; Soil Microbiology ; Universities And Colleges
    ISSN: 0167-8809
    Source: Cengage Learning, Inc.
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  • 3
    Language: English
    In: Science of the Total Environment, 15 August 2016, Vol.562, pp.1044-1053
    Description: In intensely cultivated regions, it is crucial to have knowledge of the leaching potential related to pesticides in agricultural production. This is especially true in countries, like Denmark, that base its drinking water supply on untreated groundwater. Since fluazifop-P-butyl (FPB) is applied to control perennial and annual weed grasses in agricultural fields, the objective of this study was to evaluate leaching of its two degradation products – fluazifop-P (FP; free acid; (R)-2-(4-(5-trifluoromethyl-2-pyridyloxy)phenoxy)propionic acid) and TFMP (5-(trifluoromethyl)-2(1H)-pyridinone) – through an agricultural field consisting of loamy soil. Drainage and groundwater samples were collected over a five-year period following four spring/summer applications of FPB, and analysed for both FP and TFMP. FP was only detected once in groundwater, whereas TFMP within the first year after the first and fourth application was detected in concentrations exceeding the value of 0.1 μg L in 100% and 24% of the drainage samples and 9% and 14% of the groundwater samples, respectively. Detections of TFMP up to 18 months after application were obtained both in the drainage and groundwater. What differentiated the first and fourth FPB applications from the two others were heavy precipitation events within one week of FPB application, which resulted in rapid transport of TFMP through the discontinuities in the soil and contributed to relatively high TFMP detections in drainage and groundwater. This study indicated that pesticide degradates like TFMP, often being more soluble than the pesticide, have a relatively high leaching potential especially associated with heavy precipitation events shortly after the application. Hence, such pesticide degradates should like in Denmark be considered “relevant” meaning that the EU value for drinking water applies to them, having its leaching potential regulatory assessed based on high quality estimations of their persistence, and be exposed to an assessment of the risk to consumers of drinking contaminated groundwater.
    Keywords: Fluazifop-P-Butyl ; Tfmp ; Leaching ; Preferential Transport ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 4
    Language: English
    In: Journal of Hydrology, 2015, Vol.521, p.498(10)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jhydrol.2014.12.018 Byline: Dan Karup Jensen, Markus Tuller, Lis W. de Jonge, Emmanuel Arthur, Per Moldrup Abstract: * We present a new approach to predict the entire SWC using limited data. * The approach considers capillarity and adsorptive contributions to obtain the SWC. * We obtained accurate prediction of SWC regardless of soil texture. * Clay, silt and organic matter contribute significantly to water adsorption. Article History: Received 23 July 2014; Revised 10 December 2014; Accepted 11 December 2014 Article Note: (miscellaneous) This manuscript was handled by Peter K. Kitanidis, Editor-in-Chief, with the assistance of J. Simunek, Associate Editor
    Keywords: Soil Moisture
    ISSN: 0022-1694
    Source: Cengage Learning, Inc.
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  • 5
    Language: English
    In: Journal of Hydrology, February 2015, Vol.521, pp.498-507
    Description: The present study proposes a new two-step approach to prediction of the continuous soil water characteristic (SWC) from saturation to oven-dryness from a limited number of measured textural data, organic matter content and dry bulk density. The approach combines dry- and wet-region functions to obtain the entire SWC by means of parameterizing a previously developed continuous equation. The dry region function relates gravimetric soil fractions to adsorptive forces and the corresponding water adsorbed to soil particles. The wet region function converts the volumetric particle size fractions to pore size fractions and utilizes the capillary rise equation to predict water content and matric potential pairs. Twenty-one Arizona source soils with clay and organic carbon contents ranging from 0.01 to 0.52 kg kg and 0 to 0.07 kg kg , respectively, were used for the model development. The SWCs were measured with Tempe cells, a WP4-T Dewpoint Potentiameter, and a water vapor sorption analyzer (VSA). The model was subsequently tested for eight soils from various agricultural fields in Denmark with clay contents ranging from 0.05 to 0.41 kg kg . Test results clearly revealed that the proposed model can adequately predict the SWC based on limited soil data. The advantage of the new model is that it considers both capillary and adsorptive contributions to obtain the SWC from saturation to oven-dryness.
    Keywords: Capillarity ; Adsorption ; Unsaturated Soil ; Water Retention ; Soil Moisture ; Geography
    ISSN: 0022-1694
    E-ISSN: 1879-2707
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  • 6
    Language: English
    In: Agriculture, Ecosystems and Environment, 15 September 2012, Vol.159, pp.9-18
    Description: ► Microbial activity decreased significantly at copper concentration ∼500 mg kg . ► Soil compression resistance had an increasing trend with copper concentration. ► Copper contaminated soils had higher amounts of water dispersible clay. ► Clay dispersibility correlated with microbial activity in a copper contaminated field. Copper (Cu) is accumulating in agricultural soils because it is an essential component of mineral fertilizers and pesticides. This could lead to toxic effects on soil macro- and micro-organisms and impact soil structure development. We investigated the effect of historical Cu contamination (〉80 years; from background concentrations up to 3837 mg Cu kg ) on soil microbial enzyme activity, physical properties and resilience to compression. Soil samples and cores were taken from a fallow sandy loam field in Denmark. Microbial activity was quantified using fluorescein diacetate (FDA) and dehydrogenase (DHA) assays. Water dispersible clay was measured on field moist and air dried samples. For the resilience assay, soil cores (drained to −100 hPa) were subjected to uniaxial confined compression (200 kPa) followed by wet–dry or freeze–thaw cycles. Microbial enzyme activity significantly decreased with Cu concentration ≳500 mg kg with the two microbial assays linearly correlated with each other as well as with the water dispersible clay. An effect concentration causing a 50% reduction (EC ) in enzyme activity was observed at 521 mg kg for FDA and 542 mg kg for DHA. Significant increases in water dispersible clay, bulk density and decreases in air-filled porosity and air permeability were observed from Cu ≳ 900 mg kg . The increased density of the contaminated soils led to greater compression resistance and resilience relative to the uncontaminated soil. The results suggest that a threshold level for Cu exists (∼500 mg kg for this soil type) beyond which microbial activity decreases and soil structure becomes more compact with reduced permeability to air.
    Keywords: Soil Contamination ; Dehydrogenase Activity ; Clay Dispersibility ; Air Permeability ; Compression ; Resilience ; Agriculture ; Environmental Sciences
    ISSN: 0167-8809
    E-ISSN: 1873-2305
    Source: ScienceDirect Journals (Elsevier)
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  • 7
    Language: English
    In: Agriculture, ecosystems & environment, 2012, Vol.159, pp.9-18
    Description: Copper (Cu) is accumulating in agricultural soils because it is an essential component of mineral fertilizers and pesticides. This could lead to toxic effects on soil macro- and micro-organisms and impact soil structure development. We investigated the effect of historical Cu contamination (〉80years; from background concentrations up to 3837mg Cukg⁻¹) on soil microbial enzyme activity, physical properties and resilience to compression. Soil samples and cores were taken from a fallow sandy loam field in Denmark. Microbial activity was quantified using fluorescein diacetate (FDA) and dehydrogenase (DHA) assays. Water dispersible clay was measured on field moist and air dried samples. For the resilience assay, soil cores (drained to −100hPa) were subjected to uniaxial confined compression (200kPa) followed by wet–dry or freeze–thaw cycles. Microbial enzyme activity significantly decreased with Cu concentration ≳500mgkg⁻¹ with the two microbial assays linearly correlated with each other as well as with the water dispersible clay. An effect concentration causing a 50% reduction (EC₅₀) in enzyme activity was observed at 521mgkg⁻¹ for FDA and 542mgkg⁻¹ for DHA. Significant increases in water dispersible clay, bulk density and decreases in air-filled porosity and air permeability were observed from Cu≳900mgkg⁻¹. The increased density of the contaminated soils led to greater compression resistance and resilience relative to the uncontaminated soil. The results suggest that a threshold level for Cu exists (∼500mgkg⁻¹ for this soil type) beyond which microbial activity decreases and soil structure becomes more compact with reduced permeability to air. ; p. 9-18.
    Keywords: Wet-Dry Cycles ; Clay ; Bulk Density ; Air Drying ; Agricultural Soils ; Soil Density ; Porosity ; Soil Sampling ; Fluorescein ; Mineral Fertilizers ; Soil Structure ; Soil Toxicity ; Soil Enzymes ; Food And Drug Administration ; Enzyme Activity ; Air ; Pesticides ; Microbial Activity ; Permeability
    ISSN: 0167-8809
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 8
    Language: English
    In: Geoderma, 2015, Vol.259-260, p.224(9)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.geoderma.2015.06.011 Byline: Marcos Paradelo, Trine Norgaard, Per Moldrup, T.P.A. Ferre, K.G.I.D. Kumari, Emmanuel Arthur, Lis W. de Jonge Abstract: Sorption is considered one of the most important processes controlling pesticide mobility in agricultural soils. Accurate predictions of sorption coefficients are needed for reliable risk assessments of groundwater contamination from pesticides. In this work, we aim to estimate the glyphosate sorption coefficient, K.sub.d, from easily measurable soil properties in two loamy, agricultural fields in Denmark: Estrup and Silstrup. Forty-five soil samples in Estrup and 65 in Silstrup were collected from the surface in a rectangular grid of 15x15-m from each field, and selected soil properties and glyphosate sorption coefficients were determined. Multiple linear regression (MLR) analyses were performed using nine geo-referenced soil properties as variables to identify the parameters related with glyphosate sorption. Scenarios considered in the analyses included: (i) each field separately, (ii) both fields together, and (iii) northern and southern sections of the field in Silstrup. Considering correlations with all possible sets of the same nine geo-referenced properties, a best-four set of parameters was identified for each model scenario. The best-four set for the field in Estrup included clay, oxalate-extractable Fe, Olsen P and pH, while the best-four set for Silstrup included clay, OC, Olsen P and EC. When the field in Silstrup was separated in a northern and southern section, the northern section included EC, and oxalate-extractable Fe, Al and P, whereas the southern part included pH, clay, OC and Olsen P. The best-four set for both fields together included clay, sand, pH and EC. Thus, the most common parameters repeated in the best-four sets included clay and pH as also reported previously in the literature, but in general, the composition of the best-four set differed for each scenario, suggesting that different properties control glyphosate sorption in different locations and at different scales of analysis. Better predictions were obtained for the best-four set for the field in Estrup (R.sup.2 =0.87) and for both fields (R.sup.2 =0.70), while the field in Silstrup showed a lower predictability (R.sup.2 =0.36). Possibly, the low predictability for the field in Silstrup originated from opposing gradients in clay and oxalate-extractable Fe across the field. Also, whereas a lower clay content in Estrup may be the limiting variable for glyphosate sorption, the field in Silstrup has a higher clay content not limiting the sorption, but introducing more variability in K.sub.d due to changes in other soil properties. Article History: Received 24 September 2014; Revised 6 May 2015; Accepted 9 June 2015
    Keywords: Glyphosate – Analysis ; Oxalic Acid – Analysis ; Agricultural Land – Analysis ; Loams – Analysis ; Oxalates – Analysis
    ISSN: 0016-7061
    Source: Cengage Learning, Inc.
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  • 9
    In: Soil Science Society of America Journal, January 2012, Vol.76(1), pp.18-27
    Description: Accurate estimation of soil gas diffusivity (/, the ratio of gas diffusion coefficients in soil and free air) and air permeability () from basic texture and pore characteristics will be highly valuable for modeling soil gas transport and emission and their field‐scale variations. From the topsoil of two Danish arable fields representing two natural clay gradients, / and were measured at soil water matric potentials between −1 and −100 kPa on undisturbed soil cores. The Rosin–Rammler particle size distribution parameters α and β (characteristic particle size and degree of sorting, respectively) and the Campbell water retention parameter were used to characterize particle and pore size distributions, respectively. Campbell yielded a wide interval (4.6–26.2) and was highly correlated with α, β, and volumetric clay content. Both / and followed simple power‐law functions (PLFs) of air‐filled porosity (ε). The PLF tortuosity–connectivity factors (*) for / and were both highly correlated with all basic soil characteristics, in the order of volumetric clay content = Campbell 〉 gravimetric clay content 〉 α 〉 β. The PLF water blockage factors () for / and were also well (but relatively more weakly) correlated with the basic soil characteristics, again with the best correlations to volumetric clay content and . As a first attempt at developing a simple / model useful at the field scale, we extended the classical Buckingham / model (ε) by a scaling factor based on volumetric clay content. The scaled Buckingham model provided accurate predictions of (ε)/ across both natural clay gradients.
    Keywords: Soils ; Aarup Denmark ; Arhus Denmark ; Buckingham Model ; Cambisols ; Connectivity ; Convection ; Denmark ; Diffusivity ; Europe ; Experimental Studies ; Gas Transport ; Grain Size ; Jutland ; Laboratory Studies ; Luvisols ; Nordjylland Denmark ; Northern Denmark ; Particles ; Porosity ; Rosin-Rammler Model ; Saeby Denmark ; Scandinavia ; Size Distribution ; Soil Gases ; Soils ; Tortuosity ; Transport ; Western Europe;
    ISSN: 0361-5995
    E-ISSN: 1435-0661
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  • 10
    In: Water Resources Research, January 2016, Vol.52(1), pp.190-205
    Description: The mathematical characterization of water vapor sorption isotherms of soils is crucial for modeling processes such as volatilization of pesticides and diffusive and convective water vapor transport. Although numerous physically based and empirical models were previously proposed to describe sorption isotherms of building materials, food, and other industrial products, knowledge about the applicability of these functions for soils is noticeably lacking. We present an evaluation of nine models for characterizing adsorption/desorption isotherms for a water activity range from 0.03 to 0.93 based on measured data of 207 soils with widely varying textures, organic carbon contents, and clay mineralogy. In addition, the potential applicability of the models for prediction of sorption isotherms from known clay content was investigated. While in general, all investigated models described measured adsorption and desorption isotherms reasonably well, distinct differences were observed between physical and empirical models and due to the different degrees of freedom of the model equations. There were also considerable differences in model performance for adsorption and desorption data. While regression analysis relating model parameters and clay content and subsequent model application for prediction of measured isotherms showed promise for the majority of investigated soils, for soils with distinct kaolinitic and smectitic clay mineralogy predicted isotherms did not closely match the measurements. Nine isotherm models for water vapor sorption in soils were evaluated Model performances differ for adsorption and desorption data Promising prediction of soil water vapor sorption isotherms from clay content
    Keywords: Hysteresis ; Adsorption ; Desorption ; Clay Content ; Gab
    ISSN: 0043-1397
    E-ISSN: 1944-7973
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